Brian Ratliff

200lb bodyweight:
109/106 for 23mm tires (Rear/Front, just above 105 and just shy of 110)
104/101 for 25mm tires (Rear/Front, just above 100 and just shy of 105)

For technical crits where I am running tubulars and there are 6+ corners, I ride 22mm tires closer to 100psi.

For track, which is a smooth surface, no corners and 2g loadings:
150-170+ (depends on tire type) psi with tubulars.

My philosophy is that there is a range of tire pressure that keeps you out of pinch flat trouble on the low side and puncture trouble on the high side. For me this range is 105-120psi for road riding on 23mm tires. Within that range, I select tire pressure based on road conditions, traction requirements, and race type, i.e. bumpy roads = lower pressure, more required traction = lower pressure, time trials = higher pressure.

There are some games with tire size you can play as well. If you are riding a gravel road and want to run lower pressure because of the bumps and terrain but want to stay above pinch flat pressure, you go wider. For instance 25mm tire on me (200lb person) can be run down to 90psi without worrying too much about pinch flats. A 28mm tire can be run down to 75psi. A 32mm cross tire can be run down to 60psi.

You can also run tubular which has the effect of basically eliminating pinch flats unless you are actually bottoming out the rim, and can usually support higher tire pressure than clinchers without bouncing around bumps as much (the glued interface is much less stiff than the beaded interface of a clincher, and the casing of a tubular can support higher tire pressure than the casing+bead interface of a clincher).

MKahrl

The chart in post #2 covers lighter and heavier riders than the Michelin chart. There is an Android app called Berto Tire Pressure based on that graph (graph originally done by Frank Berto, back when Bicycling! magazine had a technical editor that actually did testing). It takes into account tire width, rider and bike weight, and front/back weight distribution.

Tom Boonen won Paris-Roubaix with 28mm tires with 60 psi supporting his 180 lbs. The majority of that race is on smooth roads; from their viewpoint the performance hit of soft tires on smooth pavement was negligible compared to the huge advantage it had on the cobblestones. Testing by Bicycle Quarterly bares this out.

coasting 

According to those charts, I underinflate. Yet I've not had a puncture in 2 years. There! I've said it. Gods of cycling, do your worst.

datlas 

Well, by the same charts, PCAD overinflates. Big time.

Draw your own conclusions.

cplager

Underinflating also leads to more rolling resistance. So it will take you more energy to ride to that first flat...

sbslider

I read that wider tires are faster, up to a point. What is that point? I suppose it depends a bit on how wide your favorite tire is made, but it seems like at some point the additional tire weight is going to slow down acceleration.

cplager

The weight of the tire counts twice as far as acceleration goes. A couple hundred grams compared to 50+ kg for total rider/bike weight, it just doesn't make that much difference.

Wider tires are less aerodynamic so there's a speed at which fatter tires become slower than skinnier tires.

Unless you're racing, going with wider tires that can handle high pressure is almost always the way to go.

superfred

There was this article claiming the optimal width for rolling resistance is 25mm. However that is countered for inferior areodynamics and heavier weight. Also current wide rims are designed to be used with 23mm tires to make a oval profile into the wind. A sharp teardrop profile seen in most tires + wheels is less efficient.

sbslider

I am not racing, and did not quite get the post from superfred. I also did not ask my question as clearly as I should have. I am currently running 25mm GP4000s tires. I really like the way they feel and handle. The GP4000s does not come in an wider width. But other tires do, and I wonder if 28s, 35s, 42s, etc. would all be potentially lower rolling resistance because they are wider. My bike can handle any of them. Perhaps the 35s and 42s are a bit of a stretch, as I suspect performance type tires are not made that big anyway.

Bottom line is I am not looking to sustain speeds of 30 mph. I am not really worried about hitting 45 mph vs 43 mph on descents due to tire aerodynamics. I don't know, but I suspect on my bike (surly cross check) that there are other aero factors that limit me before my tires. I am interested in climbing hills faster, and if possible getting 22-23 mph out of my flat land ride with the present energy I am putting in for 19-20 mph.

waterrockets 

Drop your bars, get aero bars, wear a skinsuit and a TT helmet, then do some terminal velocity testing to tune the position. Tires are not going to make up that difference.

Without any changes to aerodynamics, on flat ground you're going to need 52% more power to go 15% faster, since power to overcome air drag increases at a cubic rate. (15% = 1.15 and 1.15 ^ 3 ~= 1.52 and 1.52 = 52%). No way any tire is going to equal a 52% power gain -- you need to get serious about aerodynamics if you want to go that much faster without more power.

sbslider

Nope, I am not that serious, just a commuter who enjoys going fast. My guess is I won't do a lot better climbing hills than with the tiers I have now, but I was intrigued by the post stating

"Tom Boonen won Paris-Roubaix with 28mm tires with 60 psi supporting his 180 lbs. The majority of that race is on smooth roads; from their viewpoint the performance hit of soft tires on smooth pavement was negligible compared to the huge advantage it had on the cobblestones."

Not so much the relatively low pressure part, but using 28m tires for racing.

gb2319

How does tubeless affect things here? Is there a baseline PSI I should be knocking off simply due to my tires being tubeless. I've been running about 10 PSI less in the front and back than I do with tubes, and it seems to work well, but I haven't been able to experiment extensively yet, either.

rodzthomas

A lot of information here. Thanks guys!

rbrsddn

You can run lower pressures without the fear of pinch flats. I am using Fusion 3's 23mm at 85 F 90 R, and I weigh around 175. The lower pressures make for a smoother ride.

dstrong 

I'm still at my "winter weight" of 205 and I run 100/90 in my 25mm GP4000s. Haven't had a pinch flat in a few years and find these pressures comfortable on the cheapseal around here.

After a flat and booting of my rear tire last year, I hand inflated because I wasn't comfortable with the repair and just wanted to get home. As I was riding, I thought "man...this is a comfortable ride!" After I got home, I discovered I had 60psi in the tire.